Calcium sequestering activity of vascular muscle sarcoplasmic reticulum is greatly reduced in experimental hypertension in rats. This is associated with an impaired rate of vascular smooth muscle relaxation, a markedly reduced maximal contractile response and evidence of a reduced intracellular calcium pool. A major objective of this project is to characterize changes in regulation of calcium ions and membrane dynamics in vascular smooth muscle during the course of experimental hypertension in rat. Membrane parameters chosen for this study include calcium pump activity of the sarcoplasmic reticulum, membrane microviscosity which modulates calcium ion movements and calcium pump activity, membrane phospholipid methyltransferase activity which rapidly modulates membrane microviscosity and calmodulin which modulates many calcium dependent activities including calcium pumps and smooth muscle contraction.